Details details

I'm exhausted!  It's been one of those phases where suddenly lots of big things are happening at the build and the space is transformed again.  The inside spaces of the bungalow are taking shape and almost all of them now have at least some kind of wall, and are more or less defined as they will be when all is done.  Over a fortnight the big thick strawclay wall went up (the main internal structure in the extension, acting as thermal mass/heat-store and soundproofing between Anna's and my workspaces), as did the also-big masonry stove that will provide us with a highly efficient and lovely source of heat.  Each of those is probably a blog by itself, so this one is about the less exciting but still crucial bits that happened before.

It's all about the details.  Everything.  Always.

Okay, maybe not actually everything, and not quite always - but a lot of times in life it's the details that define something or lift it from barely passable to something wonderful.  It's definitely true of the build.  Paying attention to the details of finish should make the home lovely to be in.  But before that there's a lot of very mundane details to resolve to ensure the building functions well and efficiently, stays warm and dry, or cool and dry and summer; that things are set up well so that later stages of the build go smoothly, with things fitting together as they should; and that the finished house is easy to live in, move around, and equipment is easy to use with switches located in sensible places (for example).

It's been said that sometimes (often?) this blog is a load of semi-technical waffle followed by a load of photos of holes.  I concede that there is some truth in this!  The rest of this blog may fall into that category, although instead of holes it'll be photos of taped-up things, air-sealing grommets, hazel pegs, and cables (and maybe one shallow hole, right near the end).

I spent what felt like far too long wondering around the bungalow sealing things up with a variety of different industrial-grade sticky-tapes.  This may well be my least-favourite activity yet, rivalled only by the shovelling and compaction of 33 tonnes of chunky (hard-to-shovel) stone into the foundations in the rain last year.  It was necessary to make the building airtight, or as airtight as possible.

Airtightness is really really important.  The most wonderfully insulating strawbale walls and deep cosy roof insulation are not much good if there's a big gap between them through which the cold wind blows.  Around 20-35% of heat loss from homes is typically through ventilation.  This includes through open windows, doors and airbricks, but also through less obvious means.  Draughts around poorly-fitting window and door frames, around cable and pipe entries into the home or through ceilings, even cracks in plasterboard ceilings or masonry walls (Greenspec have a helpful diagram with more info about airtightness and heat loss here) all allow warm air out, and cold air in.  Attention to detail to seal up these points of leakage is essential to create an energy-efficient building.

Airtightness does bring it's own problems.  Many of the problems of dampness in buildings stem from moisture in the air condensing on cold surfaces.  Ventilation is necessary to remove the damp air from the house.  The common way to deal with damp areas is basically to make a hole in the wall (or window frame) and cover it with a grille.  This is effective at removing the moisture, it's very simple to do, but is also very effective at removing a large amount of heat.  The other problem with airtight homes is a lack of fresh-air and oxygen.  This is all avoided by use of a ventilation system with heat recovery.  This (unsurprisingly) recovers heat from air being removed from the home and puts it back into the air coming into the home.  We have opted for a ducted whole-house Mechanical Ventilation system with Heat Recovery (MVHR).  This uses a low-power fan to extract air from the dampest rooms (kitchen, bathroom, anywhere with a sink or a loo, entrance room with wet coats) and supply air to all the other rooms (or sometimes the other end of the same room).  The supply air and extract air pass through a heat-exchanger which recovers around 90% of the heat which would otherwise be lost.  The components of this are now onsite, a worryingly large 3D jigsaw for me to piece together sometime soon.

Any kind of combustion heating is a problem with an airtight home.  Whether it's a gas boiler or a woodburning stove, it needs air to burn cleanly and safely, without running the risk of carbon monoxide poisoning.  Building regs require a permanently open air vent for a stove in an airtight house.  Again, normally this would be a hole in a wall, which renders completely pointless all that painstaking work to thoroughly insulate the building and prevent draughts.  So the stove will have it's own dedicated air-supply, channelled directly into it and separated from the room.

The next blog will have more pretty pictures and less explanation.  Maybe.

Sheepswool insulation stuffed into gap between foundation walls and timber baseplate.  Also filling notches for compression straps used to compress the bale walls (see http://thewoodlouse.blogspot.co.uk/2012/08/bale-frenzy-part-2-hairy-bungalow.html)

Airtightness detailing: holes around metal wall-ties taped over, membrane strip glued and stapled in place to seal potential air-leakage point between brick and bale walls

No good having a well-sealed window if the frame isn't sealed well to the building.  Despite silicone sealant around the frames on the outside I could feel the air blowing through around the frame.  The tape eradicated that.

MVHR (heat-recovery ventilation) ducting and fittings, looming at me.

Once again, ready for vampire attack.

Electric fittings stage 1, 2 and 3: trim back the straw where light-switch or electric socket will go, hammer in hazel pins, cover straw with clay-slip

Electric fittings stage 4: level (and fireproof) the area with clay-plaster (clay and chopped straw)

Electric fittings stage 5: Screw smartply OSB offcut to the hazel pins.  This allows a bit of flexibility when fitting the switch/socket boxes, meaning they can positioned exactly where needed.  Much easier than trying to place the hazel pins perfectly.

LSF (Low Smoke and Fume) PVC-free cable. PVC is a very polluting material, in production and disposal (http://www.healthybuilding.net/pvc/ThorntonPVCSummary.html), responsible for chlorine and dioxin release.  It also releases highly toxic fumes in the unlucky event of a fire.  PVC-free cable is also tougher, which is an added bonus.

Justin the electrician hasn't totalled up the distance yet but we think there's around 2 km of cable in the building now, for sockets, lighting and switching, and data.  Shocking how quickly it adds up.

And finally: socket back box fitted to OSB, pinned into straw

Home-made airtightness grommet (EPDM rubber-roofing offcut) where cables come through recycled-paper airtightness membrane in the ceiling.

Cabling in the Bat Loft

There's a hole in my wall...

Now there's an LED light filling it

Very discrete external LED light fittings they are too.

Boxing for an MVHR duct, under sunny windows.  I'm really liking the sun this year.

One of those "doesn't look much but feels momentous" moments - waterpipe finally persuaded to get around some awkward bends in the service duct linking the outside rainwater harvesting tank with the house.

And at the the other end...

Ta-da!  One pipe supplies rainwater to the header-tank in the loft, the other will dump it back into the underground tank if we go away (the water will go stagnant in the warmer loft but will stay clear and nice in the cool, dark underground tank).

An opened up bale demonstrating the behaviour of water and rot if you get a leak through bales (in this case via rubbish tarpaulin covering spare bales throughout the wettest year on record in England).  The water drains straight through the straw, and only the area immediately below the leak rots.  If this happens in a wall the rot can be cut out and new straw stuffed in.

Making more of a mess of the floor, in order to fit air-supply for masonry stove

Air supply pipe to another dimension

Floor repaired, insulating (and strong, and recycled) foamglas slab fitted, with NHL lime screed on top, air pipe in centre, ready for stove.

Finally, a footnote about electric cables and strawbale walls.  Despite the beliefs of almost any electrician, and even a few green-builders, you do not need to use armoured cable in strawbale walls!  This idea seems to have spread via Grand Designs and Ben Law's otherwise amazing build in Sussex.  The idea is that mice or other animals might like to live in the straw, then might nibble through the cable-covering, then an electric spark might trigger an almighty, home-destroying blaze.

There are a couple false assumptions here.  Firstly the mice: they probably would like to make a bed in straw, but are equally - if not more - likely to nest in any loose insulation materials, such as are commonly used in walls and ceilings through which cables often run.  If the bale walls are built properly there is nowhere for mice to get into the bales.  The bales are dense, compressed and compacted, and completely covered in plaster or render.  Secondly the fire risk: strawbale walls have been tested and found to exceed the bulding regs requirements for fire resistance many times, withstanding fire for 2 hours 40 minutes before a fail (smoke penetration from one side to the other - still not a fire).  Strawbale construction has been approved for bushfire areas of Australia (pdf link).  In any case, the cables are run on the surface of the straw wall in conduit which is then completely encased in clay-plaster.

I'm sure I'll return to the subject of strawbale and the perceived fire risk - it's a myth that needs some serious busting!

'Natural' isn't necessarily 'sustainable'

naturally occurring asbestos

When choosing materials to use in our build we try to choose the most sustainable.  Sustainable living means making best use of available resources, aiming for the smallest negative environmental and social impact possible.  This is more complicated than simply using 'natural' materials.

I think the terms 'natural building' or 'natural materials' are unhelpful.  The presumption is that natural is good, artificial is bad.  'Natural' is often used interchangeably with 'sustainable'.

Even before questioning whether it's accurate to conflate natural with sustainable, there's a whole philosophical debate to be had about what is or isn't natural.  For example my preferred building material is strawbale, which is often called natural.  It's the dried out stalk of a plant - something that grew - so of course it's natural.  Really?  But it's also the product of machine-dependant industrial agriculture, a mono-crop that wouldn't occur on the same scale without human intervention.  Following that train of thought I ask: at what point does human activity stop being natural?  We're products of nature; maybe anything we do is natural.  But that would soon render the term fairly all-encompasing and so meaningless in any helpful way.  Or is human-made unnatural, and everything else natural?

Natural materials are often seen to be either those things that grew (plant-based), or other things which occur in a useful form (like stone or slate).  In reality, both will usually have had to undergo some form of processing.

Straw has been compressed and bound up in to a more-or-less regular shape, the machine-made bale.  Strawbales might not fit a definition of 'natural', but they do fit my idea of sustainable.  It's using a waste product.  Despite the oil burned by farm machinery strawbales are generally held to be carbon negative - there is more carbon locked up in their structure than has been released in their manufacture and transport (and if the straw was left to rot, that carbon would be released back into the atmosphere, which it is not whilst the bales remain part of our walls).

Stone has been quarried, usually by machines, and transported large distances.  On an industrial scale quarrying can be very harmful to the landscape and there can be issues with polluted water run-off from the quarries.  Seen like that I think it looks a lot less sustainable.  It's a scale though: stone is certainly more sustainable than cement, which has a much higher amount of carbon associated with it's manufacture, and more harmful pollutants.

Slate is a fine 'natural' material.  The processing is minimal.  If sourced locally and on a small scale it could be sustainable (the same applies to stone).  But much roofing slate these days is imported from Brazil, in which case the carbon and pollution caused by its transport stops it being sustainable.

Is natural necessarily good anyway?  There are many examples of highly toxic, natural things.  Here are just two: Deadly Nightshade is a naturally occurring plant - which as the name suggests, really is deadly if you eat it; Asbestos is a naturally occurring mineral - but the World Health Organisation estimates that 107 000 people die each year from asbestos-related lung cancer, mesothelioma and asbestosis resulting from occupational exposure to asbestos.

On that cheerful note I'll end this shortish rant.  For ease I do sometimes describe materials as natural, but I've been increasingly finding it rankles.

Emerging from the dark winter

My last post was three months ago. I'm not doing very well at regularly updating this blog, am I?  I've just been too tired and unmotivated to sort it out in the evenings or weekends.  The cold, dark bit of the winter seemed to be going on for an awfully long time.  With the roof of the bungalow and extension still uninsulated and endless ways for wind to get into the building, it got and stayed pretty cold in there.  Fine when waving bits of timber and a nailgun around to build stud-walls but not so good when lying on the floor stuffing sheepswool insulation into gaps, or fitting the last bit of guttering with a light snow falling.  The project management side of things suffered a bit through the darker winter months as well.  The last thing I felt like doing in the evenings was sitting at the computer.  I probably could have moved things on a bit more if I'd been more on the ball.

At the end of March it was a year since we started, and another revised estimated date of completion rolled cheerfully by without much sign of a moving in date.

But now Spring is here and this year it really feels like spring.  The psychological benefits are remarkable!  Things are moving forward steadily on site.  Right now the first-fix electrics are being installed (photos in next blog), cables all over the place.  Once that's done the next lot of transformative jobs can begin.  Getting the timber frames up for the internal walls up a while ago was great, it suddenly felt like the whole place might yet become habitable.

At some point in the next month or so I hope to build the main dividing wall in the extension, which will be thick straw-clay, to provide an acoustically insulated barrier between Anna's studio and my office so we can both make noise and work at the same time without irritating each other.  I'm looking for volunteers interested in helping mix up the straw and clay, before lightly ramming it into shuttering to form the wall.  It's a relatively light mix - much more straw than clay - but forms strong walls when dry.  It also acts as a good thermal store and the clay in it helps to regulate moisture levels (as does the clay plaster which will cover it and all the strawbale walls) by absorbing excess moisture which then evaporates when humidity levels drop.

Anyone who might be interested in volunteering for the strawclay wall, and/or also for clay plastering which I hope will follow shortly after, please send me your contact details and I'll get in touch when I have dates.  Email: johnbeebutler @ gmail . com (without the spaces, obviously), or get me on twitter: @the_woodlouse

Hopefully the next blog will be soon, I already have enough photos for it.

Without roof insulation and draft sealing - it got pretty cold in there

The old bathroom and kitchen wall finally knocked down.  I put up a temporary bathroom wall shortly after, for reasons of privacy

New solatubes fitted.  Cutting holes in the watertight roof covering felt very wrong.

The solatub dome is sealed to the roof with roofing sealant, but I got the EPDM roofers to seal around it with their sealing tape as well, when they cam back to fix a couple of leaks (where seams hadn't sealed properly first time)

The last bit of guttering finally in place

Shiny new nails for shiny new nailgun

With the aid of wonderful mitre saw, I fitted the lower row of rafters which will hold the ceiling up, creating a void to fill with insualtion.

Me in the loft, looking like a fool (Brimmed hat to stop spiders dropping down my neck, fleece hat for warmth)

Woodfibre insulation, fitted to the wall above ceiling height in the old bungalow - the idea is to help reduce thermal-bridging (heat loss through heat being conducted up the brickwork from the living space)

And similar at the other end of the loft, here also to prevent heat loss from the extension (with its higher ceiling level) into the loft.  The black tank will be the header tank for the rainwater harvesting system - from which the loos will be flushed.

Here will be a door...

The snail of acoustic vibration control

Vertical timber 'studs', with the foam-rubber on each end.  This limits transfer of sound-vibrations through the structure, helping Anna and me make noise in our respective spaces without annoying each other.

Saw position not seeming so clever now I've built the wall.

studs and base-timbers separated by foam

Clay slip coating the straw before end wall-stud is fitted.  The first stage of clay-plastering will be to cover all exposed straw with clay slip in the same way.

Finished studwork and the nailgun that made it possible (or at least, very much quicker)

Chocolate contemplates Anna contemplating internal bathroom window options

The section at the front of the bungalow that is remaining as brick outside.  This is insulated internally with Thermafleece sheepswool, in timber frame.  This is the first layer

High-tech solution for cutting sheepswool insulation to size - two cramps, some wood and a breadknife

The second layer of sheep

And the final layer.  The inward opeining hinges of the window are too close to the edge of the frame to be able to insulate that little bit of wall next to it.  That will be a thermal bridge (althouth there is still cavity insulation between it and the outside) - I wish we'd foreseen this and planned around it, but hopefully we won't lose too much heat that way.  It's a good example of one reason we wouldn't quite meet Passivhaus criteria, as they are meant to be virtually thermal bridge free.  Much harder to achieve in retrofit.

Final layer of insulation complete, first bit of VCL going on - Vapour Control/airtightness Layer/membrane to prevent moisture getting into the insulation and causing potentially harmful condensation

Recycled-paper Airtightness/Vapour control layer complete around the internal insulation.  Battens to hold plasterboard and create void through which electric cables can be fitted.

Internal sheepswool insulation by the front door

And VCL/airtightness over it.

Plasterboard fitted to walls by front door - this area needs finishing earlier than everywhere else so that electric consumer-unit (fusebox) and meter can be fitted there.

First coat of bonding plaster to even up levels over brickwork next to doorframe.

My first proper plastering, so satisfying.  I love plastering, would love it more if someone else was mixing the stuff up for me.  I also really like the way it transforms a messy collection of boards into a unified solid-looking mass.